362 research outputs found
(μ-4,4′-Bipyridine-κ2 N:N′)bis[bis(N,N-dimethyldithiocarbamato-κ2 S,S′)zinc(II)]
The title dinuclear ZnII complex, [Zn2(C3H6NS2)4(C10H8N2)], is centrosymmetric; the mid-point of the C—C bond linking the two pyridine rings is located on an inversion center. The pyridine N atom coordinates to the ZnII cation, which is also chelated by two dimethyldithiocarbamate anions, giving a trigonal-bipyramidal ZnNS4 geometry. Weak intermolecular C—H⋯S hydrogen bonding is present in the crystal structure
Virtualizing Reconfigurable Architectures: From Fpgas To Beyond
With field-programmable gate arrays (FPGAs) being widely deployed in data centers to enhance the computing performance, an efficient virtualization support is required to fully unleash the potential of cloud FPGAs. However, the system support for FPGAs in the context of the cloud environment is still in its infancy, which leads to a low resource utilization due to the tight coupling between compilation and resource allocation. Moreover, the system support proposed in existing works is limited to a homogeneous FPGA cluster comprising identical FPGA devices, which is hard to be extended to a heterogeneous FPGA cluster that comprises multiple types of FPGAs. As the FPGA cloud is expected to become increasingly heterogeneous due to the hardware rolling upgrade strategy, it is necessary to provide efficient virtualization support for the heterogeneous FPGA cluster.
In this dissertation, we first identify three pairs of conflicting requirements from runtime management and offline compilation, which are related to the tradeoff between flexibility and efficiency. These conflicting requirements are the fundamental reason why the single-level abstraction proposed in prior works for the homogeneous FPGA cluster cannot be trivially extended to the heterogeneous cluster. To decouple these conflicting requirements, we provide a two-level system abstraction. Specifically, the high-level abstraction is FPGA-agnostic and provides a simple and homogeneous view of the FPGA resources to simplify the runtime management and maximize the flexibility. On the contrary, the low-level abstraction is FPGA-specific and exposes sufficient low-level hardware details to the compilation framework to ensure the mapping quality and maximize the efficiency. This generic two-level system abstraction can also be specialized to the homogeneous FPGA cluster and/or be extended to leverage application-specific information to further improve the efficiency. We also develop a compilation framework and a modular runtime system with a heuristic-based runtime management policy to support this two-level system abstraction. By enabling a dynamic FPGA sharing at the sub-FPGA granularity, the proposed virtualization solution can deploy 1.62x more applications using the same amount of FPGA resources and reduce the compilation time by 22.6% (perform as many compilation tasks in parallel as possible) with an acceptable virtualization overhead, i.e.,
Finally, we use Liquid Silicon as a case study to show that the proposed virtualization solution can be extended to other spatial reconfigurable architectures. Liquid Silicon is a homogeneous reconfigurable architecture enabled by the non-volatile memory technology (i.e., RRAM). It extends the configuration capability of existing FPGAs from computation to the whole spectrum ranging from computation to data storage. It allows users to better customize hardware by flexibly partitioning hardware resources between computation and memory based on the actual usage. Instead of naively applying the proposed virtualization solution onto Liquid Silicon, we co-optimize the system abstraction and Liquid Silicon architecture to improve the performance
catena-Poly[cadmium-bis(μ-N,N-dimethyldithiocarbamato-κ3 S,S′:S)]
In the title compound, [Cd(C3H6NS2)2]n, the CdII atom, lying on a twofold rotation axis, is coordinated by six S atoms from four different N,N-dimethyldithiocarbamate ligands in a distorted octahedral geometry. The bridging of S atoms of the ligands leads to the formation of a one-dimensional structure along [001]
The thermal and electrical properties of the promising semiconductor MXene Hf2CO2
In this work, we investigate the thermal and electrical properties of
oxygen-functionalized M2CO2 (M = Ti, Zr, Hf) MXenes using first-principles
calculations. Hf2CO2 is found to exhibit a thermal conductivity better than
MoS2 and phosphorene. The room temperature thermal conductivity along the
armchair direction is determined to be 86.25-131.2 Wm-1K-1 with a flake length
of 5-100 um, and the corresponding value in the zigzag direction is
approximately 42% of that in the armchair direction. Other important thermal
properties of M2CO2 are also considered, including their specific heat and
thermal expansion coefficients. The theoretical room temperature thermal
expansion coefficient of Hf2CO2 is 6.094x10-6 K-1, which is lower than that of
most metals. Moreover, Hf2CO2 is determined to be a semiconductor with a band
gap of 1.657 eV and to have high and anisotropic carrier mobility. At room
temperature, the Hf2CO2 hole mobility in the armchair direction (in the zigzag
direction) is determined to be as high as 13.5x103 cm2V-1s-1 (17.6x103
cm2V-1s-1), which is comparable to that of phosphorene. Broader utilization of
Hf2CO2 as a material for nanoelectronics is likely because of its moderate band
gap, satisfactory thermal conductivity, low thermal expansion coefficient, and
excellent carrier mobility. The corresponding thermal and electrical properties
of Ti2CO2 and Zr2CO2 are also provided here for comparison. Notably, Ti2CO2
presents relatively low thermal conductivity and much higher carrier mobility
than Hf2CO2, which is an indication that Ti2CO2 may be used as an efficient
thermoelectric material.Comment: 26 pages, 5 figures, 2 table
Diaquabis{2-hydroxy-5-[(pyridin-2-yl)methylideneamino]benzoato-κ2 N,N′}zinc(II) dihydrate
The complex molecule of the title compound, [Zn(C13H9N2O3)2(H2O)2]·2H2O, has 2 symmetry with the ZnII cation located on a twofold rotation axis. The Zn cation is N,N′-chelated by two 5-[(pyridin-2-yl)methylideneamino]-2-hydroxybenzoate anions and coordinated by two water molecules in a distorted octahedral geometry. Within the anionic ligand, the pyridine ring is oriented at a dihedral angle of 49.54 (10)° with respect to the benzene ring. The carboxylate group of the anionic ligand is not involved in coordination but is O—H⋯O hydrogen bonded to the coordinated and uncoordinated water molecules. Weak intermolecular C—H⋯O hydrogen bonding is also present in the crystal structure
Diaquabis{2-hydroxy-5-[(pyridin-2-yl)methylideneamino]benzoato-κ2 N,N′}nickel(II) dihydrate
In the title complex, [Ni(C13H9N2O3)2(H2O)2]·2H2O, the NiII atom, located on a twofold rotation axis, is in a distorted octahedral geometry, defined by four N atoms from two 2-hydroxy-5-[(pyridin-2-yl)methylideneamino]benzoate ligands and two O atoms from two water molecules. In the crystal, intermolecular O—H⋯O hydrogen bonds link the complex molecules and uncoordinated water molecules into a three-dimensional network. Intramolecular O—H⋯O hydrogen bonds are present between the hydroxy and carboxylate groups
Bis(1,10-phenanthroline-κ2 N,N′)[2-(4-sulfonatoanilino)acetato-κO]copper(II) dihydrate
In the title compound, [Cu(C8H7NO5S)(C12H8N2)2]·2H2O, the CuII ion is coordinated by four N atoms from two 1,10-phenanthroline (phen) ligands and one O atom from a 2-(4-sulfonatoanilino)acetate (spia) ligand in a distorted square-pyramidal geometry. Intermolecular N—H⋯O and O—H⋯O hydrogen bonds, as well as π–π interactions between phen ligands and between phen and spia ligands [centroid–centroid distances = 3.663 (3), 3.768 (3) and 3.565 (3) Å], result in a three-dimensional supramolecular structure
A new family of semifields with 2 parameters
A new family of commutative semifields with two parameters is presented. Its
left and middle nucleus are both determined. Furthermore, we prove that for any
different pairs of parameters, these semifields are not isotopic. It is also
shown that, for some special parameters, one semifield in this family can lead
to two inequivalent planar functions. Finally, using similar construction, new
APN functions are given
Head-to-Tail: How Knowledgeable are Large Language Models (LLM)? A.K.A. Will LLMs Replace Knowledge Graphs?
Since the recent prosperity of Large Language Models (LLMs), there have been
interleaved discussions regarding how to reduce hallucinations from LLM
responses, how to increase the factuality of LLMs, and whether Knowledge Graphs
(KGs), which store the world knowledge in a symbolic form, will be replaced
with LLMs. In this paper, we try to answer these questions from a new angle:
How knowledgeable are LLMs?
To answer this question, we constructed Head-to-Tail, a benchmark that
consists of 18K question-answer (QA) pairs regarding head, torso, and tail
facts in terms of popularity. We designed an automated evaluation method and a
set of metrics that closely approximate the knowledge an LLM confidently
internalizes. Through a comprehensive evaluation of 14 publicly available LLMs,
we show that existing LLMs are still far from being perfect in terms of their
grasp of factual knowledge, especially for facts of torso-to-tail entities
Bis(μ-2-phenylquinoline-4-carboxylato)-κ3 O,O′:O;κ3 O:O,O′-bis[(2,2′-bipyridine-κ2 N,N′)(2-phenylquinoline-4-carboxylato-κ2 O,O′)cadmium(II)]
The neutral binuclear title complex, [Cd2(C16H10NO2)4(C10H8N2)2], is centrosymmetric, with the inversion center generating the central (μ-O)2Cd2 bridge. The CdII ion is in a strongly distorted CdN2O5 pentagonal-bipyramidal geometry, defined by two N atoms from one 2,2′-bipyridine ligand and five O atoms from three 2-phenylquinoline-4-carboxylate ligands, one monodentate, two bidentate. Weak intermolecular π–π interactions [centroid–centroid distance = 3.712 (3) Å] help to establish the packing of the structure
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